[B+C] Add Ban Reason to "Vanilla" Bukkit - Fixes BUKKIT-4813

**The Issue:**
Currently, there is no way to see a ban reason and banning player with using an external plugin.

**Justification:**
By having 1 less plugin to install this will increase (not by much) the server speed of many servers as they will no longer have to write to the databases that they use to store their own bans (which if they are using external servers, can become very laggy for muiltiple write requests)

**Breakdown:**
[C]This just added the required methods to keep current system working as well as new bans.
[B]This added the required changes to the ban command to parse reason and banning player.

**Testing:**
Compiled server and started banning users with random reasons. Checked banned-players.txt for verification.
Also banned some with no reason to test if both options work.

**Relevant PR(s):**
https://github.com/Bukkit/CraftBukkit/pull/1250

**JIRA Ticket:**
https://bukkit.atlassian.net/browse/BUKKIT-4813
https://bukkit.atlassian.net/browse/BUKKIT-4285 - Not mine but suits